This invention pertains to a novel class of sulfonated organophosphine compounds and their use as ligands in metal-ligand complex catalysts that are capable of catalyzing hydroformylation processes.
Hydroformylation processes are well known in the art, for example, as described in “Applied Homogeneous Catalysis with Organometallic Compounds,” edited by B. Cornils and W. A. Herrmann, VCH, New York, 1996, vol. 1, pp. 29-104. Hydroformylation involves conversion of an olefinically-unsaturated reactant with carbon monoxide and hydrogen (syngas) to produce one or more corresponding formyl-substituted products (aldehydes). Hydroformylation processes are known to be catalyzed by metal-ligand complex catalysts, preferably, a transition metal-organophosphorus ligand complex catalyst. Representative art disclosing hydroformylation catalysts comprising a variety of triorganophosphine, triorganophosphite, diorganophosphite, and bisphosphite ligands is found in the following reference “Rhodium Catalyzed Hydroformylation,” edited by P. W. N. M. van Leeuwen and C. Clayer, Kluwer Academic Publisher, USA Edition, 2002. If desired, the formyl-substituted products can be subjected to downstream functionalization processes, for example, reduction of the aldehyde to form an alcohol; or reductive amination of the aldehyde to from an amine; or oxidation of the aldehyde to form a carboxylic acid; or aldolization of the aldehyde followed by oxidation to form an hydroxyacid. Alcohols, amines, carboxylic acids, and hydroxyacids obtained via hydroformylation of an olefinically-unsaturated reactant find utility as solvents, surfactants, and monomers for the preparation of polymers, and as intermediates in the synthesis of pharmaceuticals and other industrially-useful chemicals. Preferably, mono-, di-, and tri-alcohols and corresponding amines obtained directly from hydroformylation can be converted via transesterification into polyester polyols and polyester polyamines, respectively, which are especially useful in the manufacture of polyurethane polymers.
The hydroformylation of long-chain olefinically-unsaturated reactants having from 6 to about 60 carbon atoms is of present day interest. In particular, one class of long-chain olefinically-unsaturated reactants comprises a mixture of mono-, di-, and tri-unsaturated fatty acids or fatty acid esters having from about 10 to about 50 carbon atoms, preferably, the olefinically-unsaturated fatty acid esters of lower alkanols, preferably, C1-8 alkanols (mono-alkanols), for example, methanol. Olefinically-unsaturated fatty acid esters of the lower alkanols are themselves derived by transesterifying a seed oil, for example, a soy, castor, or canola vegetable oil, with the C1-8 alkanol. Thus, seed oils can provide a renewable alternative feedstock of olefinically-unsaturated fatty acids or fatty esters, which is capable, in part, of replacing petroleum in the manufacture of industrially-useful chemicals.
More specifically, the present day hydroformylation of olefinically-unsaturated fatty acids or fatty esters and other long chain olefinically-unsaturated compounds is conducted in a rhodium-catalyzed one-phase process containing a water-soluble ionic ligand, preferably, an alkali metal salt of a dihydrocarbylarylphosphine monosulfonate compound wherein the hydrocarbyl comprises an alkyl or aryl group, and further containing a solubilizing solvent, such as N-methyl-2-pyrrolidinone (NMP), as disclosed for example in WO 2004/096744. Separation of the resulting aldehyde-containing reaction product fluid is advantageously effected by addition of water, as disclosed for example in U.S. Pat. No. 5,180,854, under conditions sufficient to obtain a non-polar phase containing one or more aldehyde products and any non-polar solvent(s) as may be present and a polar phase containing the rhodium-ligand catalyst, optional free ionically-charged ligand, water, and solubilizing solvent. Disadvantageously, ligands containing an aryl-phosphorus bond tend to undergo alkyl-aryl exchange during the course of hydroformylation by way of reaction of the phosphine ligand with the olefinically-unsaturated compound, as disclosed in U.S. Pat. No. 4,283,304 and by A. G. Abatjoglou, et al., in Organometallics, 1984, 3, 923-926.
Ligand alkyl-aryl exchange generates three undesirable results. First, alkyl-aryl exchange consumes the particular species of ligand active in the hydroformylation process, which then needs to be replaced. Second, alkyl-aryl exchange produces non-ionic or neutral ligands, which are insoluble in water and which can remain along with coordinated rhodium complexes in the non-polar phase containing the aldehyde product(s) rather than being extracted into the polar phase. Third, alkyl-aryl exchange produces sodium benzenesulfonate, which accumulates in the polar phase and can eventually precipitate onto the walls of the reactor equipment and foul the same. Sodium benzenesulfonate may also induce undesirable separation of the water/NMP polar phase.
In view of the above, a search continues to discover novel compounds that can be utilized as ligands in transition metal-ligand complex catalysts for the hydroformylation of olefinically-unsaturated compounds, particularly, unsaturated fatty acids and fatty esters and other long-chain olefinically unsaturated compounds. It would be desirable for such novel compounds to provide for comparable or better olefin conversion and product selectivity, as compared with prior art organophosphorus ligands. Moreover, it would be desirable for such novel compounds to provide for improved ligand stability with reduction of alkyl-aryl exchange, as compared with prior art ligands.
U.S. Pat. No. 5,773,666 discloses a hydroformylation process using P(X1)(X2)(X3—SO3M) as a ligand, wherein X1 and X2 are monovalent hydrocarbon groups with 1-15 carbon atoms, X3 is a divalent hydrocarbon group with 1-15 carbon atoms, and M is an alkali metal. In the description and working examples of U.S. Pat. No. 5,773,666, X3 is disclosed to be specifically 1,3-phenylene or a tri- or tetra-methylene, such that the phenylene or the tri- or tetra-methylene is substituted with a sulfonate group.
U.S. Pat. No. 5,180,854 discloses sulfonated organophosphine ligands of the following generic formula:
wherein R3 represents a divalent alkylene radical having from 2 to 12 carbon atoms or a divalent 1,3-phenylene radical. Preferably, when R3 is a divalent alkylene radical, R3 has from 2 to 5 carbon atoms; more preferably, R3 is, 1,3-propylene or 1,4-butylene.
T. Barak, et al. discloses in Organometallics, 12 (1993), 164-170, water-soluble phosphines prepared by sulfonating one or more phenyl groups on a tri(aralkyl)phosphine of the formula P[(CH2)x(C6H5)]3, wherein x is 1, 2, 3, or 6.
U.S. Pat. No. 4,625,068 and U.S. Pat. No. 4,642,388 disclose the use of non-ionic tricycloalkylphosphines, such as tricyclohexylphosphine, in hydroformylation of internal olefins or hindered terminal vinylidenes, respectively.